Hybrid vehicles use multiple propulsion systems (gasoline and electric, battery powered motors) to provide motive power. When cruising or idling, some of the output of the combustion engine is fed to a generator (merely the electric motor(s) running in generator mode), which produces electricity to charge the batteries. These hybrid vehicles also recharge their batteries by capturing kinetic energy via regenerative braking. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrid vehicles still require gasoline as their fuel source though diesel and other fuels such as ethanol or plant based oils have also seen occasional use.
Electric batteries and cells comprise electrodes and an ion conducting electrolyte positioned between them. Battery packs that contain lithium ion batteries are increasingly popular with automotive applications and various commercial electronic devices because they are rechargeable and have no memory, effect. Operating the lithium ion battery at an optimal operating temperature is very important to the batteries performance and lifespan.
Due to the characteristics of lithium ion batteries, they are typically specified to operate-within an approximate ambient temperature range of −30° C. to 60° C. However, even when operating within this temperature range, a battery pack may begin to lose its capacity or ability to charge or discharge should it remain at the extremes for long periods of time. Nonetheless, it may be unavoidable that the lithium ion battery be used where the ambient temperature falls outside the temperature range.
Significant temperature variances can occur from one cell to the next, which is detrimental to performance of the battery pack. To promote long life of the entire battery pack, the cells must be below a desired threshold temperature. To promote pack performance, the differential temperature between the cells in the battery pack should be minimized. However, depending on the thermal path to ambient, different cells will reach different temperatures. Further, for the same reasons, different cells reach different temperatures during the charging process. Accordingly, if one cell is at an increased temperature with respect to the other cells, its charge or discharge efficiency will be different, and, therefore, it may charge or discharge faster than the other cells. This will lead to a decline in the performance of the entire pack.
The art is replete with various designs of the battery packs with cooling and packaging systems. For example, U.S. Pat. No. 5,071,652 to Jones et al. teaches a metal oxide-hydrogen battery including an outer pressure vessel of circular configuration that contains a plurality of circular cell modules disposed side-by-side.
There is a need for an improved battery assembly with improved cooling and heating system adaptable to maintain the battery assembly at the optimal operating temperature to ensure the longest possible life cycle, with rated capacity, and charge and discharge rates.